1. Field of the Invention:
This invention relates to 1,2-naphthalocyanine derivatives serving as near-infrared absorbents which are used as optoelectronic materials, as well as optical recording media, near-infrared absorption filters and display materials using such near-infrared absorbents.
2. Description of the Prior Art:
In recent years, near-infrared absorbents are being used as optoelectronic materials in the manufacture of optical recording media, optical cards, laser printers, near-infrared absorption filters, goggles and the like.
Conventionally known near-infrared absorbents include cyanine dyes (Japanese Patent Laid-Open Nos. 46221/'81 and 112790/'83), phthalocyanine dyes (Japanese Patent Laid-Open No. 36490/'83), naphthoquinone dyes (Japanese Patent Laid-Open No. 15458/'85), anthraquinone dyes (Japanese Patent Laid-Open No. 291651/'86) and dithiol complexes (Japanese Patent Laid-Open No. 175693/'83).
However, these conventional dyes have major disadvantages. Specifically, cyanine dyes are insufficient in fastness properties such as light resistance and thermal resistance. The absorption wavelength range of phthalocyanine dyes is as short as 600-700 nm. Anthraquinone and naphthoquinone dyes have a low molar extinction coefficient of the order of several tens of thousands. Dithiol complexes are insufficient in thermal stability and molar extinction coefficient.
Moreover, 2,3-naphthalocyanine dyes, which are analogous to the near-infrared absorbents of the present invention, have an absorption band at 750 to 800 nm in the dissolved state and absorb light from semiconductor lasers. However, when they are in the form of a film or solid, their absorption band is shifted and the absorption of light (in the wavelength range of 780 to 830 nm) from semiconductor lasers is diminished.